Air handling systems, whether residential, commercial, or municipal, typically use a blower to urge air of a predetermined temperature through a duct system to control and maintain the temperature of an enclosure. The blower typically includes a fan operationally connected to a motor. The motor is typically electric. The air handling system is typically required to provide air flow under a variety of conditions, including variable enclosure volume, the temperature of the enclosure, the temperature of the air delivered, the duct geometry, and the like.
Typically, an air handling system is required to provide air at a constant flow rate. A constant flow rate is generally achieved by controlling the speed of the driver motor in response to detected changes in the air flow rate and/or related variables. A number of control paradigms have been developed to control air flow rate by controlling motor speed, the specifics of each tailored to the characteristics of the hardware, desired output, and building environment of the particular air handling system in question.
Typically, the electric motor driving the blower fan is a synchronous and operating at fixed increments of speed, such as 600 RPM, 900 RPM, 1800 RPM, 3600 RPM and the like. In order to effectively operate synchronous motors at speeds other than their incremental options, the motors must be connected to the blower fan via an adaptor, such as a V-belt or the like, whereby the motor speed may be relatively smoothly stepped up or down as desired. The drawback of this approach is that such adaptor systems are somewhat inefficient, costing the system extra energy. Further, such systems contribute to increased noise output and the requirement of sound insulation, more powerful electronic controller capability, and additional control and feedback modules.
Further, the standard electric motors and blowers of existing air handling systems are designed to more or less efficiently operate around a narrow plateau of operating speeds and are typically designed to most efficiently operate around the speeds correlating to the standard and most common air flow demand. When demand spikes, it becomes very inefficient and even stressful to the system to ramp up to meet the sudden increase in demand for air flow, if the motor can even accommodate the demand at all. Thus, it is often necessary to have several independent and redundant air handling systems in place to handle acute, unusually heavy demands. For example, water treatment plants have two, and sometimes three, separate air handling systems in place to handle increased water demand due to heavy rainstorms or morning and evening heavy load times. The drawback of this configuration is that energizing the redundant blower unit often supplies more air flow than is required for the process, resulting in unneeded power consumption. Alternatively, an induction motor and VFD can be used, to adjust the blower airflow and meet process demands However, induction motors operate at less than their optimum efficiency when run at less than full motor load. Also, these motors have a relatively steep efficiency drop as motor speed moves away from the optimal. Finally, there is an added cost to supplying and maintaining several independent blower units for one job.
Thus, there is a need for an air handling system having a motor capable of directly providing variable output speeds and a method and apparatus for controlling the same to optimize the efficiency of the air handling system while providing a constant air flow output. The present novel technology addresses these needs.